Blends of acetylenic hydrocarbons



BLENDS OF ACETYLENIQ HYDROC f 1 No Drawing. Application May 21, 1956,Serial No. 586,329

1 Claim. c1. 52-5 This invention relates to improvements in propellants,and more particularly pertains to improvements in acetylenichydrocarbons for use as rocket fuels.

It is well known that various jet propulsion devices including bothmonopropellant and bipropellant rocket systems and ram jets, haveassumed great importance in recent times. The subject is of everincreasing importance in jet propulsion systems as used in airplanes,guided and unguided missiles, and jet-assisted takeoff units.

Generally, the fuels that can be used for these purposes can beclassified roughly into three categories. These three categories consistof the low performance type, the intermediate performance type, and thehigh performance type. Examples of the low performance type include thekerosene and refined petroleum fractions and the simple alcohols such asethyl alcohol. These fuels are low in cost but they have relatively lowspecific impulse, or driving force, and they are not hypergolic; thatis, they do not ignite spontaneously with the oxidizing agents withwhich they are employed commonly. At the other extreme, the jet fuelshaving very high specific impulse, such as diborane and the like, arevery expensive, diflicult to produce, and are generally quite toxic.

Although pure acetylenic hydrocarbons having prohibitively high meltingpoints cannot be used as liquid fuels, by blending these high meltingpoint materials with particular other acetylenic hydrocarbons of lowermelting point, desirable blend characteristics can be obtained, therebyretaining a major portion of the advantageous features of bothcomponents. By suitably selecting the components and proportions of suchblends, the stability characteristics of the blend to storage overprolonged periods of time and to elevated temperatures, as well as theirshock sensitivity, can also be improved materially.

A principal object of this invention is to provide a blend of acetylenichydrocarbons for use as rocket fuels.

Another object is to provide such a blend having practical logistics,boiling and freezing points, vapor pressure, viscosity, density,specific impulse, heat of combustion, flame velocity, stability,ignition, corrosion and metal salts formation, and toxicitycharacteristics.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same ice becomes better understood byreference to the following detailed description.

An acetylenic hydrocarbon having good ignition properties is dimethyldivinyl diacetylene, 2,7-dimethyl 1,7 octadiene 3,5-diyne, having thestructural formula Tests of this compound indicated the high ignitionrating of 8 with hexane dilution and 7 with benzene dilution. However,the compound has several undesirable characteristics. Its freezing pointis 23 F., and it exhibits a high degree of instability towardsmechanical and thermal shock. Its mechanical shock sensitivity is 80% onthe drop weight impact test, one of the highest ratings of acetylenichydrocarbons, and it bursts into flame when subjected to thermal shock.

Methyl vinyl acetylene, Z-methyl l-butene 3-yne, having the structuralformula has a very low freezing point, lower than l12 F., and a highheat of combustion, 19,680 B. t. u. per pound. It is also far morestable than dimethyl divinyl diacetylene, standing at 40% on the ratingscale. Further, it is much cheaper to manufacture than the dimethyldivinyl diacetylene. Methyl vinyl acetylene is further characterized byan ignition rating of 5 with hexane or benzene dilution.

A 30% mixture of dimethyl divinyl diacetylene in methyl vinyl acetyleneremained liquid at 40 F. This blend has an ignition rating of 7 withhexane dilution, and 6 with benzene dilution, an appreciable improvementover the 5 rating of methyl vinyl acetylene with both dilutions. Theimpact shock rating of the blend is substantially less than the ratingof the dimethyl divinyl diacetylene.

The blend described thus provides an acetylenic hydrocarbon rocket fuelhaving an ignition rating almost as good as that of the originaldimethyl divinyl acetylene, as well as substantially improved shockresistance making feasible its use for the purposes intended.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claim the invention maybe practiced otherwise than as specifically described.

We claim:

An acetylenic hydrocarbon rocket fuel consisting of a 30% mixture ofdimethyl divinyl diacetylene in methyl vinyl acetylene.

References Cited in the file of this patent UNITED STATES PATENTS2,573,471 Malina et al Oct. 30, 1951 2,702,984 Britton et al Mar. 1,1955

